Process for the production of alkenylpyridines and catalyst therefor



United States Patent 3,119,828 PROCESS F912 THE PRQDUCTION UF ALKENYL-PYRIDHNES AND CATALYST THEREFQR Jean Herzenberg, Guidobaldo Cevidaili,and Adriano Nenz, all of Pv llilfilll, Italy, assigucrs to SicedisonS.p.A., Milan, Italy No Drawing. Filed Aug. 11, 1959, gex'. No. 832,894Claims priority, application Etaly et. 14, 1958 2 Claims. (Cl. 260290)The present invention relates to a process for the production ofal-kenybpyridines and particularly to a process wherein specialcatalysts are used.

As already known, a dehydrogenation reaction of alkylpyridines for theproduction of =alkenyl-pyridines is carried out by conductingalkyl-pyridme vapors, suitably diluted with inert gases or steam, over asolid catalyst, at temperatures ranging from 550 C. to 700 C. Under suchconditions, the dehydrogenation reaciton is associated withdealltylation and isomerization reactions, as well as with othersecondary reactions by which the starting material is broken down andthere is obtained in addition to the desired main product, lower boilingalkyl-pyridiues and gaseous by products, with the added dnawback of theformation of carbon products which contaminate the catalyst. Followingknown procedures there is a relatively low yield of the desired product,together with a swift and progressive inhibition of the catalyst.

It is an object of the present invention to provide a process for theproduction of alkenybpyridines by the dehydrogenation of alkyl-pyridinesin the gaseous phase, by means of a solid catalyst.

A further object or" the invention consists in the production ofalkenyl-pyridines by the dehydrogenation of alkyl-pyridines with highconversion ates.

A further object of the invention consists in suppressing the formationof byproducts as, for example, the dealkylation products in adehydrogenation process converting alkyl-pyridines intoalkenyl-py-ridines thereby insuring the efficient and profitableoperation of the process.

Further advantages to be realized by the means and method according tothe present invention will become apparent from the followingdescription.

According to the present invention, all pyridine homologues having oneor more ethyl, propyl, or butyl groups, which may be furthersubstituted, in the second, third, fourth, fifth, or sixth positions ofthe pyridine ring, may be dehydrogenated, with good yields, to formalkenylpyridines. It has hitherto been known that 2-methyl-5- ethylpyridine can be dehydrogenated to 2-methyl-5-vinyl pyridine by the useof iron oxides, as catalysts together with small amounts of alkali andchromium oxides. It has been hound that using oxides of metals accordingto the second gnoup, second subgroup, of the periodic system, andparticularly zinc oxide, as the essential part of the catalyst, highlyactive catalysts can be obtained, permitting operation at lowertemperatures, with high specific yields of methyl-vinyl-p-yridine pervolume unit of catalyst. Even better results have been obtained with acatalyst prepared the addition of small amounts of A1 0 CaO, K 0 and CrO to Zinc oxideairon oxide mixtures. Such catalysts are highlyselective, in that the dehydrogenation reaction will predominate overthe dealkylation reaction, and the undesired further secondaryreactions.

Good results have been obtained, for example, from a catalyst composedof ZnO 50-80 percent, Fe O' 10-30 percent, CaO 1-15 percent, A1 0 5-10percent, K 0 1-5 percent, and Cr O 0.5-2 percent. :The catalyst may bereadily prepared in the conventional manner, that is, by employing purezinc and calcium oxides mixed with Al(0'l-l) Cr(OH) and Fe(OH)co-precipitated from Patented Jan. 28, 1964 their sulfates by the actionof NH To the composition thus obtained, there may be added aconcentrated KOH solution, and the product finally submitted to anovendrying operation until the consistency required for extrusion hasbeen attained. The extruded rods are out into small cylinders andoven-dried at temperatures ranging from 700-750 C. in a stream ofnitrogen. The latter operation is particularly important in thepreparation of the catalyst suitable for the operation of the processaccording to the present invention. However, recourse may also be had toother methods for the prepara tion of the catalyst. it is found that thepresence of oxide results in the dehydrogenation reaction being mademore selective, thereby possible a high yield also at lowertempcratiu'es, and facilitating operation at a higher space velocity ofthe reagents. The presence of 08.0 and K 0 markedly promotes the Watergas reaction, thereby preventing the precipitation of carbon onto thecatalyst, the activity whereof is thus kept constant for a longer periodotitime. The activity of the catalyst is materially increased by thepresence of iron, aluminium and chromium oxides in the above-statedproportions.

In the technical operation of the process, the product to bedehydrogeuated may be suitably diluted before the start of the reaction,with an inert gas or steam. The use of steam is beneficial in that, dueto its high specific heat; it exerts a temperature stabilizing action inthe differeut parts of the catalyst, thereby protecting the organicmolecule from secondary reactions. Moreover, the presence of steam hasthe desirable etiect of decreasing the partial pressure of the substanceto be dehydnogenated thereby shifting the thermodynamic balance of thereaction in the required direction. Further, a chemical action isexerted by the steam on any possibly occurring tarry residues, whichotherwise would tend to deposit onto the catalyst, whereby they areconverted into carbon dioxide and hydrogen, thus materially extendingthe active life of the catalyst. In this respect it has been found thatthe catalyst should be characterized by a specific activity in promotingthe reaction, whereby the tarry residues are converted into carbondioxide and hydrogen, extending the life of the catalyst for thedehydrogenation reaction. The catalysts used in the process 'accordingto the present invention, displays these desirable ieatures and, as willhereinattcr be shown (note Example HI), an amount of water only two orthree times greater by Weight than the alkyl-py-ridine, is sufiicient toobtain a very good activity and selectivity of the catalystwithoutnecessity of employing greater dilutions.

According to the present invention, the dehydrogenation can be carriedout in a temperature range of 500 C. to 800 C., preferably 550 C. to 650C. In order to prevent secondary reactions, it is found to be advantageous to employ steam which has been first superheated up to atemperature in the range of substantially 700 C. to 850 C., thealkyl-pyridine vapors being introduced into the catalyst zone withoutany overheating. For instance in the temperature zone: 550-620 C., thecatalyst will show a sufiiciently high dehydrogenating activity and atthe same time strongly restrains secondary reactions. Moreover, at thesame temperatures a considerable oxidizing action is exerted by thesteam on the carbon formations, to the extent that no traces of carbonmay be found on the catalyst even after many hundred hours of operation.

The space velocities, expressed as units of gas volume, taken at 0 C.and 760 mm. Hg, that flow across a volume unit of catalyst per hour,adopted in this process for the mixture of alkyl-pyridinc and steam,range between 5,000 and 20,000 volume units per volume unit of catalyst,per hour, which corresponds to an unusually high production ofalkenyl-pyridine per volume unit of catalyst.

In order that the process according to the present invention may befully understood, the following detailed examples are given. In theseexamples three types of catalysts are specified, and for each theresults are set forth operating under different specific operatingconditions. It will be noted that the basic components, zinc oxide andiron oxide, are present in all of the catalysts used and that thepresence and the amounts of activators differ in the several examples.The influence exerted by the said activators on the activity and theselectivity of the catalysts, will be readily appreciated by thoseskilled in the art. Following the present description, furtherpossibilities of variation will become apparent to those skilled in theart.

It is understood that, following the present description, these examplesare only of an illustrating and not limiting purpose.

EXAMPLE I (a) Preparation of Catalyst Pure ZnO in the amount of 800grams is mixed with an aqueous solution containing 14 grams of KOH,forming thereby a mixture of pasty consistency. To this mixture there isadded a precipitate containing Fe(OH) and Cr(OH) obtaining by treating asolution containing 630 grams of Fe (SO .9H O and 34.8 grams PercentZ110 8O F8203 1 8 K 1.2 C110 8 (b) Dehydrogenation 320 grams of thecatalyst, prepared as above described, is introduced into stainlesssteel reactor tube (V4A-, 35 mm. diameter) wherein the volume occupiedby the catalyst will be about 240 cu. cm. The catalyst-loaded reactortube is heated in an electric mutiie furnace up to reaction temperature.Steam, superheated in another electric furnace to a temperature up toabout 700 0, together with 2-methyl-5-ethyl pyridine vaporized in asmall separate vaporizer, is introduced into the reactor tube and heldat reaction temperature as hereinafter specified with a variation ofplus or minus 1 or 2 degrees C.

In the subjoined table there are set forth the operating conditions andresults corresponding to two runs, one being at a dehydrogenationtemperature of 580 C. and the other at a temperature of 600 C. Thevapors discharged from the reactor tube are condensed in a highefficiency water condenser and the resulting liquid is submitted to ade-gasing operation in a degasifier connected with a gas meter. The rawreaction product forms two layers: the upper organic rich layer having awater content of 18-19 percent, and a lower aqueous layer con taining upto 2 percent of pyridine bases. The upper or organic phase is separated,subjected to dehydration and admixed with the chloromethylen extractobtained from the aqueous phase, and distilled in a suitabledistillation column. The obtained fractions are analyzed. The gasesobtained in the dehydrogenation run are also measured and analyzed. Theresults, tabulated below, have been obtained from an average sample ofreaction products, the test in each case representing a 24 hour run.

1st Test 2d Test Dehydrogenation temperature, C7 580 600 Weight ofcatalyst, grams 320 318 Vohune of catalyst, cu. cm 240 240 Weight; feedrate of MEP, grams/hr 303 303 Weight feed rate of H20, grems/hr 2,000 2,000 Mole ratio water/MEP 44. 4 4G. 2 Weight ratio water/MEP 6. 6 0.0Space velocity (v./v./h.):

MEP gas (0 C. and 760 mm. Hg) 23 230 H2O gas (0 C. and 760 mm. Hg).10,400 10, 400 MEP liquid 1. 35 1. 37 I120 liquid 8. 37 8.35 Vol. ofobtained gases: l./l1r. at 0 C. and 760 mm. Hg. 53 82 Balance ofmaterials, percent 98. 8 07. 4 Conversion (percent mol) 37. 8 53. 1 Perpass yield 01 MVP (percent mol, mol 01 led MEI). 31. B 42. 0 Ultimateyield of MVP (mol percent, mol of converted MEP) 84. 2 70. 2 Yield ofLow Boiling 1 (average M percent, mol of converted MEI). 7.8 10. 5 Yieldof High Boiling (percent g o 2 Yield of carbon in the gases (percent g.,g. 01 converted 4 7 6 8 Analysis of gases (vol. percent): 9 1 0 CO 15. 217. 6 CH4 2. 5 1. 8 02H; and higher .8 .8 N2 2.2 3.0 Hz 78. 4 75. 8

1 For the terms Low Boiling and High Boiling sec explication,

column 5.

EXAMPLE II (a) Preparation 0 Catalyst A catalyst is prepared similarlyto Example I, with the only difference that a mixture of CaO and ZnO isadded to the iron and chromium hydrates. The composition of the catalystthus prepared is as follows:

Percent ZnO 76 Fe203 CaO 4 K 0 1.2 Cr O The calcium oxide serves todecrease the tendency of the catalyst to produce secondary reaction,i.e. to increase the selectivity toward the desired dehydrogenationreaction- (b) Dehydrogenation 151: est 2d 'lest Dehydrogenatlontemperature, C 600 600 Volume of catalyst, cu. em 240 240 Weight ofcatalyst, grams 290 284 Weight feed rate of MEP, grams/hr 305 159 Weightfeed rate of H10, grams/hr--. 2, 090 1,060 Molar ratio HzO/MEP 40. 0 44.8 Weight ratio flO/ JEP 6. 6. 66 Space velocity (v./v./hr.):

MEP gas (0 C. and 760 mm. Hg) 235 122 H2O gas (0 C. and 760 mm. Hg)-10,800 5, 500 MEP, liquid- 1.33 .72 B 0, liquid- 8. 7 4. 42 97. s 90. 0Conversion (percent mol) 41. 8 60. 6 Per pass yield of M P (percent molmol of red MEP). 37. 1 51. 0 Ultimate yield of MVP (percent m0 mol ofconverted LIEP 00. 3 84.0 Ultimate yield of Low Bolling" (average M.W.=)

(percent mol, mol of converted MEP) 4.2 7, 5 Ultimate yield of HighBoiling" (percent g., g. of

converted MEP) .6 .6 Volume of obtained gases (0 C. and 760 mm. Hg)L/hr. 51 49 Yield of carbon in the gases (percent g g of converted ME 4.1 5. 4 Analysis of gases (vol. percent):

CO 7 l. l C On 13. 2 15. 0 CH1 3. 5 2. 4 0 H and higher 1.0 1.1 N 3. 53. 0 78.1 70. 5

5 EXAMPLE III (a) Preparation of Catalyst 600 grams of pure ZnO and 140grams of pure CaO are mixed with the precipitate obtained as set forthin Example I, starting from a solution of 530 grams Fe (SO .9H O, 520grams of Al (SO .18H O, and 35 grams of Cr (SO .15H O. The compositionas obtained after the addition of a saturated solution of KOH,containing 26 grams of KOH, is extruded as described in Example I. Bythis procedure there is obtained approximately 1 kilogram of catalysthaving the following composition.

Percent (b) Dehydrogenation 200 grams of the catalyst above described issubjected to dehydrogenation tests carried out as in Examples I and II,Z-methyLS-ethyl-pyridine. being the substance subjected todehydrogenation. The results obtained at different temperatures are setforth in the subjoined tabulation.

1st 2d 3d 4th 5th Test Test Test Test Test Dehydrogenation temp, C 600600 610 630 660 Volume of catalyst, cu. cm- 240 240 180 240 240 Weightof catalyst, grams 202 208 155 210 212 Weight feed rate of MEP, gramshr- 158. 4 309. 6 298 567 545 Weight feed rate of H 0, gramslhr 1,0522,025 1, 550 1,983 2, 130 Molar ratio HzQ NIEP 44. 7 44 35 23. 5 26. 2Weight ratio HzO/MEP 6.65 6.58 5.17 3. 5 3. 91

Space velocity v /hr:

lEP gas (C., 760 mm) H2O gas (0 C 760 mm MEP liquid. .716 .4 .8 .57 2.47 E 0 liquid.. 4. 39 8. 44 8. 62 8. 27 8. 87 Balance of materials,percent. 97.9 99.4 90.2 98.00 99.8 Conversion (percent, mol) 65.0 53.152.0 52.2 73.0 Per pass yield of MVP (percent mol, mol of fed MEP) 53. 345. 6 45. 9 44.1 54. 4 Ultimate yield of MVP (percent mol,m0lofconverted MEP) 82.0 86.0 88.3 84.5 74.5 Yield of Low Boiling (averageM.P.=110) (percent mol, mol of converted MEI 5. 8.1 9.3 7.0 12.6Ultimate yield of High Boiling (percent g., g. of converted MEP). .2 .6.5 .6 1.1 Volume of obtained gases lJhr. (at

0 C. and 760 mm. Hg) 48.5 69 71 182 352 Yield of carbon in the gases(percent g., g. of converted MEP). 5. 5 4. 2 5.0 7. 2 12.1 Analysis ofgases (vol, percent):

In the dehydrogenation examples as noted above, all products with aboiling point lower than that of methylethyl-pyridine have beentabulated under the heading Low Boiling. These products includepyridine, alphapicoline, beta-picoline, 3-ethyl pyridine, and2,5-dimethyl pyridine.

EXAMPLE IV Dehydrogenation of 4-ethyl-pyridine is carried out employingthe same catalyst as in Example III under two "erent sets of conditions.The operating conditions and the results obtained are tabulated below.

The byproducts obtained from the dehydrogenation of 4-ethyl pyridine t04-vinyl-pyr-idine, which in the table below are shown by thedesignation: Low Boiling, consist of small amounts of pyridine andgamma-picoline, for which an average molecular weight of 91 has. beenassumed.

1st 2d Test Test Dehyclrogenation temperature, C 600 620 Volume ofcatalyst, cu. em 240 160 W eight of catalyst grams 210 147 Weight feedrate of 4-ethyl-pyridine, grams/hr 140.3 182. 8 Weight feed rate ot'H O,grams/hr 1,062 1,383 Molar ratio H O/4-ethy1-pyridine 45 45 Weight ratioHgO/4-ethyl-pyridine 7. 57 7. 57 Space velocity (v./v./hr.):

4-etl1yl-pyridine (gas) (at 0 C. and 760 mm. Hg) 122. 5 239.1 11 0 (gas)(at 0 C. and 760 mm Hg) 5, 506 10,752 4-othyl-pyridine (liquid) .5841.142 11 0 (liquid) 4.425 8.64 Balance of materials, per 100 Conversion(percent, mol)--. 49. 9 37 Per pass yield of 4-vinyl pyridine (percentmol, mol of ied 4-ethyl-pyridine) 32.1 31. 2 Ultimate yield of4-vinyl-pyridine (percent mol, mol of converted 4-ethyl-pyridine) H...64. 3 84.3 Ultimate yield of low boiling (average M.W.=91)

(percent mol, mol of converted 4-ethyl-pyridine)..- 26. 4 10. 7 Ultimateyield of high boiling (percent g., g. of

converted ethyl-pyridine) .1 Volume of obtained gasesL/hr. (0 C. and 760mm. Hg) 41. 6 29. 2 Cracked 4-etl1ylpyridine (percent mol, mol ofconverted 4-ethyl-pyridine) 9. 2 4. 9 Analysis of gases (vol. percent):

CO 1. 4 1 C0 17.2 10.4 CH4 l. 8 2 CZH4 and higher 1.2 1 N 3.. 5. 4 8 H372. 6 76. 8

EXAMPLE V Dehydrogenation of 4-methyl-5-ethyl-pyridine, more generallyknown as beta collidine, is carried out employing a catalyst similar tothat described in Example 111, under conditions set forth in thesubjoined table, together with the obtained results. The byproducts thatare formed by the dehydrogenation, whereby there is formed4-methy1-5-viny1-pyridine, consist of gamma-picoline, 4,5-dimethyl-pyridine, 3-viny1-pyridine and 3-ethyl-pyridine. Thesebyproducts are indicated by the title Low Boiling, for which an averagemolecular weight of has been assumed.

Dehydrogenation' temperature C.-- 600 Volume of catalyst cu. cm.-- 240Weight of catalyst grams 210 Weight feed rate of beta-collidine---grams/hr 162.3 Weight feed rate of H 0 do 0,100 Molar ratio HO/beta-collidine 45.4 Weight ratio H o/beta-collidine 6.79 Spacevelocity (v./v./hr.):

Beta-collidine (gas) at 0 C. and 760 mm.

Hg) 125.2 H O (gas) (at 0 C. and 760 mm. Hg) 5,700 Balance of materialpercent 98.4 Conversion (percent mol.) 58 Per pass yield of4-methyl-5'-vinyl pyridine (percent mol, mol of convertedbeta-collidine)"percent" 45.5 Ultimate yield of 4 methyl 5 vinylpyridine (percent mol, mol of converted beta-collidine) percent 78.5Ultimate yield of Low Boiling (avenage h/LW.

=110) (percent mol; mol of converted betacollidine) percent 10.7Ultimate yield of High Boiling (percent g, g. of

converted beta-collidine) "percent" .4 Volume of obtained gases l./hr.(at 0 C. and

Analysis of gases (vol., percent):

Z 3-ethyl-pyridine, 2-methyl-5-propyl-pyridine, 2,4-diethylpyridine,2,5-diethyl-pyridine, are utilized in place of 4- ethyl-pyridine,2-methyl-5-ethyl-pyridine and 4-methyl-5- ethyl-pyridine in the abovespecified processes, and with one of the above-stated catalysts, withoutmaking any change thereto, high yields of the corresponding vinylderivatives are obtained.

It will be understood that the foregoing description is to beinterpreted as illustrative of the invention and not in a limitingsense.

What is claimed is: 3

.1. A process for the production of alkenyl-pyridine from alkyl-pyridinecomprising: subjecting a vaporized mixture, heated to a temperatureranging from 500 C. to 800 C., of alkyl-pyridine and steam, todehydrogenation in the presence of a catalyst, consisting of zinc oxidein amount ranging from 50 to 80 percent, iron oxide in amount rangingfrom 10 to 30 percent, chromium oxide in amount ranging from 0.5 to 2percent, an alkali metal oxide in amount ranging from 1 to 5 percent,calcium oxide in amount ranging from 1 to 15 percent, and aluminum oxidein amount ranging from 5 to percent, said percentages being referred tothe dry weight of the total amount of said catalyst.

2. A process for the production of alkenyl-pyridine from alkyl-pyridinecomprising: subjecting a vaporized mixture, heated to a temperatureranging from 500 C. to 800 C., of alkyl-substituted pyridine selectedfrom the class consisting of 2-ethyl-pyridine, S-ethyl-pyridine,4-ethyl-pyr idine, 2-methyl-S-ethyl-pyridine, 4-methyl-5-ethyl-pyridine, 2,4-diethyl-pyridine, 2,5-diethyl-pyridine and2-methyl-5-propyl-pyridine, and steam, to dehydrogenation in thepresence of a catalyst consisting of: zinc oxide in amount ranging fromto percent, iron oxide in amount ranging from 10 to 30 percent, chromiumoxide in amount ranging from 0.5 to 2 percent, an alkali metal oxide inamount ranging from 1 to 5 percent, calcium oxide in amount ranging from1 to 15 percent, and aluminum oxide in amount ranging from 5 to 10percent, said percentages being referred to the dry weight of the totalamount of said catalyst.

References Cited in the file of this patent UNITED STATES PATENTS2,611,769 Hays Sept. 23, 2,716,119 Cislak Aug. 23, 1955 2,728,770 MahanDec. 27, 1955 2,732,376 Wagner Jan. 24, 1956 2,769,811 Mahan Nov. 6,1956 2,866,790 Pitzer Dec. 30, 1958 2,888,499 Pitzer et a1. May '26,1959 2,908,655 Keith Oct. 13, 1959 OTHER REFERENCES Shuikin et al.:Chem. Abstracts, vol. 47, col. 6234 (1953).

Gusev et al.: Chem. Abstracts, vol. 49, col. 8584 (1955).

Sakuyama et al.: Chem. Abstracts, vol. 52, col 4069 (1958).

1. A PROCESS FOR THE PRODUCTION OF ALKENYL-PYRIDINE FROM ALKYL-PYRIDINECOMPRISING: SUBJECTING A VAPORIZED MIXTURE HEATED TO A TEMPERATURERANGING FROM 500*C. TO 800*C., OF ALKYL-PYRIDINE AND STEAM, TODEHYDROGENATION IN THE PRESENCE OF A CATALYST, CONSISTING OF ZINC OXIDEIN AMOUNT RANGING FROM 10 TO 30 PERCENT, CHROMIUM OXIDE IN AMOUNTRANGING FROM 0.5 TO 2 PERCENT, AN ALKALI METAL OXIDE IN AMOUNT RANGINGFROM 1 TO 5 PERCENT, CALCIUM OXIDE IN AMOUNT RANGING FROM 1 TO 15PERCENT, AND ALUMINUM OXIDE IN AMOUNT RANGING FROM 5 TO 10 PERCENT, SAIDPERCENTAGES BEING REFERRED TO THE DRY WEIGHT OF THE TOTAL AMOUNT OF SAIDCATALYST.